This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our previous work with actively stained mouse brains has allowed us to see the cytoarchitecture down to 20 microns. But, our understanding of the sources of contrast at this level of resolution is quite primative. The goal of this project is to understand more fully the sources of contrast of the cytoarchitecture in the actively stained mouse brain using the 9T MR magnet. 1. We will acquire quantiative T1 and T2 maps of the mouse brain at 40 microns with accompanying higher resolution spin echo (T1-weighted) images for definitiation of the cytoarchitecture. 2. We will histologically section the same brains and register the resulting datasets to produce 3D optical sectioned data with Nissle and Cresyl violet. 3. MR and optical sections will be registered into single volumes. 4. The resulting data will be used to define the specific sources of contrast in the most critical regions of the actively stained brain.